As with many things Japanese, it is traditional that a kumihimo
braider sit seiza in front of the marudai. Seiza is not kneeling, as
some believe. It looks much the same, but you are supposed to be
sitting on your feet and ankles. For a Westerner raised to sit in
chairs, this position is difficult and painful. If done for long
periods of time, the feet and lower legs suffer from a lack of
circulation and often "go to sleep".

As with many things Japanese, the world has developed ways for
Westerners to cheat.

Angled Seiza Bench

This low bench keep your butt up off your feet for comfort,
but keeps your butt and legs at the angle they would be if you
were sitting seiza properly.

There's a bit more detail (but not much) at
the Seiza Bench
project page.